A quantitative assessment of fish passage efficiency Michael J Noonan, James W A Grant & Christopher D Jackson Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, Canada, H4B 1R6, Correspondence: Michael J Noonan, Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, Canada, H4B 1R6 Tel.: (514) 848 2424 Ext. 4027 Fax: (514) 848 2424 Ext. 2881 E-mail: m_noona@live.concordia.ca Alternate Titles Assessing the effectiveness of fishways and other passage facilities Assessing the current state of fishways and other passage facilities Running Title Effectiveness of fish passage facilities Main Text Abstract In an attempt to restore the connectivity of fragmented river habitats, a variety of passage facilities have been installed at river barriers. Despite the cost of building these structures, 1 there has been no quantitative evaluation of their overall success at restoring fish passage. We reviewed articles from 1960 to 2011, extracted data from 65 papers on fish passage efficiency, size and species of fish, and fishway characteristics to determine the best predictors of fishway efficiency. Because data were scarce for fishes other than salmonids (order Salmoniformes), we combined data for all non-salmonids for our analysis. On average, downstream passage efficiency was 68.5%, slightly higher than upstream passage efficiency of 41.7%, and neither differed across the geographical regions of study. Salmonids were more successful than non-salmonids in passing upstream (61.7 versus 21.1%) and downstream (74.6 versus 39.6%) through fish passage facilities. Passage efficiency differed significantly between types of fishways; pool & weir, pool & slot, and natural fishways had the highest efficiencies, whereas Denil and fish locks/elevators had the lowest. Upstream passage efficiency decreased significantly with fishway slope, but increased with fishway length, and water velocity. An information theoretic analysis indicated that the best predictors of fish passage efficiency were order of fish (i.e. salmonids > non-salmonids), type of fishway, and length of fishway. Overall, the low efficiency of passage facilities indicated that most need to be improved to sufficiently mitigate habitat fragmentation for the complete fish community across a range of environmental conditions. Keywords Conservation, dams, fishways, habitat fragmentation, migration, passage efficiency 2 ________________________________________________________________________ Introduction Methods Literature search Data analysis Statistical analysis Results Discussion Acknowledgements References ________________________________________________________________________ Introduction Habitat loss and fragmentation are the major threats to both terrestrial and aquatic biodiversity, including freshwater fishes (Andrén 1994; Fahrig 1997; Larinier 2001). Given the linear nature of freshwater habitats, dams and weirs act as anthropogenic barriers that fragment the river, obstructing the movement of organisms and nutrients, and reducing the amount of available habitat for fishes (Poff and Hart 2002; Sheer and Steel 2006). Indeed, more than half of the world’s largest river systems are currently negatively affected by dams (Nilsson et al. 2005). These barriers have frequently been implicated in the decline of resident and anadromous fish populations due to their 3 negative effects on upstream adult migration (Caudil et al. 2007) and downstream migration by juveniles and adults (Wertheimer and Evans 2005; Arnekleiv et al. 2007). Indeed, habitat loss is the most important threat to endangered freshwater fishes in Canada, and infrastructure such as dams and impoundments are the most important human activity causing the loss of habitat (Venter et al. 2006). Even when upstream passage has been satisfactory, other negative effects of dams include a delay in migration in a wide variety of fish species (Haro and Kynard 1997; Lucas and Frear 1997; Moser et al. 2000, 2002; Karppinen et al. 2002; Keefer et al. 2004; Zigler et al. 2004; Hasler et al. 2011)(, higher energetic expenditures during migration (Tiffan et al. 2010), and a failure to reach the spawing grounds (Gowan et al. 2003). In an attempt to counteract the negative effects of habitat fragmentation, a wide variety of devices have been installed at river barriers to restore connectivity, and aid with both upstream and downstream fish migration (Clay 1995). Two of the most common devices to assist upstream migration are fishways, structures that allow fish to swim upstream under their own effort, and fish locks/elevators, devices that lift the fish over obstructions (Clay 1995). Downstream devices include physical screens, angled bar racks, and surface bypasses, intended to divert juveniles from passing downstream via the turbines (Larinier 2001). The design of these fishways and lifts has largely focused on economically important, anadromous species, and as a result many non-target species are not able to fully ascend the structure (Office of Technology Assessment 1995). Even well designed facilities will vary in their effectiveness depending on inter-individual differences in in swimming behaviour (Hinch and Bratty 2000; Castro-Santos 2005, and 4 physiological condition of the fish (Pon et al. 2009; Hasler et al. 2011). In addition, a large number of fishways still prevent or delay the migration of target species (Gowans et al. 2003; Boggs et al. 2004a & 2004b; Keefer et al. 2004) due to the lack of sufficient flow to attract fish to the entrance (hereafter, attraction flow), unsuitable entrance location, inadequate maintenance, and/or poor hydraulic conditions, which are not designed to aid the target species (Larinier 2001). Therefore, the presence of a fishway may not fully mitigate the fragmentation induced by a river barrier (Roscoe and Hinch 2010). Evaluating a fishway’s efficiency after construction is crucial to ensure the structure is serving its purpose, and to make necessary adjustments (Clay 1995; Roscoe and Hinch 2010). Numerous summaries on how to design an effective fishway exist (e.g. Clay 1995; Odeh 1999; Larinier 2002), but there has only been one qualitative analysis of the effectiveness of fishways (Roscoe and Hinch 2010). Roscoe and Hinch (2010) identified the major questions addressed concerning fishway design, including the efficiency with which individuals were able to pass a fishway, as well as the biological, environmental, or structural mechanisms affecting passage. In addition, they described trends in fishway publications and concluded that the focus of research has not changed significantly over time. The purpose of our study was to complement their analysis by quantifying the efficiency of fishways at providing upstream and downstream passage for fishes. Specifically, we quantified the passage efficiency of different species and sizes of fish in relation to the type of passage facility and its specific design characteristics, including its height, gradient, length, and water velocity through the structure. 5 Methods Literature search An extensive literature search for articles using the search terms ‘fishway’, ‘fishpass’, ‘fish bypass’, ‘fish’, ‘dam’ and ‘passage’ was previously conducted by Roscoe and Hinch (2010) via the ISI Web of Knowledge, and Aquatic Sciences and Fisheries Abstracts (for more details see Roscoe and Hinch 2010). The 96 peer-reviewed articles identified by their search criteria were used for this study, supplemented with 26 articles published since June 2008, obtained using the same search terms and the ISI Web of Knowledge. These articles encompassed both up- and downstream movement of fish through dedicated passage facilities across 61 dams/obstructions found in 20 countries from North America (30 dams/obstructions), Europe (24 dams/obstructions), South America (3 dams/obstructions), and Australia (4 dams/obstructions) (see references with asterisks). Included were articles from 1964 to 1 January 2011. For each study, we recorded the following information, when available: migration direction, river, dam/obstruction of study, fishway type (see below), technical characteristics of the fishway, including length, width, height, mean water depth, slope, and mean water velocity of the fishway, sample size (i.e. number of fish), and mean length of all fishes recorded in the study. While it is clear that hydraulic characteristics vary markedly within a fish passage facility (e.g. Hinch and Bratty 2000), detailed information was unavailable for most facilities. These values were compared against the species, life-stage, migration time, attraction, entrance, and passage efficiencies, fallback percentage, and passage times of their respective studies. For the purpose of this study, 6 attraction efficiency was defined as the percentage of potential migrants that was able to locate the fishway entrance (Aarestrup et al. 2003), whereas entrance efficiency was the percentage at the fishway entrance, that enter a fishway (Evans et al. 2008). Passage efficiency was defined as the percentage of fish present which entered, and successfully moved through a fishway (Larinier 2001) and encompassed both attraction and entrance efficiency. Passage time was defined as the time elapsed since first detection within the vicinity of the tailraces of a dam to the moment of successful fishway exit (Caudill et al. 2007). Fallback was defined as the percentage of fish that pass back downstream via spillways, turbine intakes, or other means, after the successful ascension of a fishway (Boggs et al. 2004). Data analysis To avoid the overrepresentation of studies with a large amount of data, or of highly studied dams, one data point per facility, per study was recorded. If a particular study had multiple data points for a single facility, a weighted average was recorded. In the case of cross study comparisons of a single facility, the median value for the facility was used as a datum in our analysis. In a few cases, efficiency values were reported as being less than zero or greater than one hundred. In these cases the values were adjusted to zero and one hundred percent, respectively. When sample sizes permitted, further analyses were conducted to determine if order of fish (see below), diel differences, geographical location, fishway type, as well as the technical characteristics of a fishway affected fishway efficiency. When a study reported data on the passage efficiency of several 7 species, one data point per species was used to evaluate the effect of fish size on passage efficiency. Fork length was converted to total length using species-specific conversion factors (www.fishbase.org). We first grouped fish by family and order for statistical analysis. Because data were scarce for all orders except for salmonids (Salmoniformes), we divided all fish into two groups: salmonids and non-salmonids. While this division is clearly arbitrary, it was useful because salmonids have higher swimming speeds than other fishes (Webb 1975), and many fishways are designed specifically for economically important salmonid species (Larinier 2001). When a study reported a significant difference in the time of day during which a species used a fishway, the preferred time of passage was recorded. Following Roscoe and Hinch (2010) we divided the studies into three geographical locations: North America, Europe and Australia/South America. Fish passage facilities designed for upstream passage were grouped into five categories: pool and weir, pool and slot, natural, Denil, fish lift/lock, and trap and truck. Pool and weir fishways were constructed as a series of small pools in steps, and required fish to swim over dividers from pool to pool (Clay 1995). Pool and slot fishways were constructed as a series of small pools in steps with openings that allowed fish to swim through dividers between pools (Clay 1995). Fishways built to resemble a natural channel, with suitable substrate, water flows, morphology, and slopes, were categorized as natural fishways (Calles and Greenberg 2005). Denil fishways included those designed as a steep flume with vanes installed to dissipate the flow and decrease velocity (Clay 1995). Fish lift/lock systems collected fish in an enclosed lock and then raised the water level to the top of the dam by the addition of water (Zilukas and Ziliukiene 2002). Trap 8 and truck installations included some form of attraction/collection system, followed by the transportation of collected fish upstream via appropriate vehicles (Schilt 2007). If a structure contained a combination of fishway types, or the types were not explicitly stated in the article, they were excluded from analyses of efficiency vs. type of fishway. Statistical analysis We could not conduct a formal meta-analysis because most studies reported the percentage of fish passing successfully through a facility without an estimate of variance (see Harrison 2011). We used analyses of variance (ANOVA), covariance (ANCOVA), Pearson’s correlations and Sign tests (=0.05) in an initial descriptive analysis of the data. The efficiency values were subjected to angular transformations for all statistical analyses. We then used an information theoretic approach (Burnham et al. 2010), using Akaike’s information criterion adjusted for small sample sizes (AICc) to identify the model that best explained the observed upstream passage efficiencies. Although statistical analyses were performed on transformed data, for visual purposes, we used the untransformed data in all figures. Results Data were scarce for fishes other than salmonids (Table 1). Hence, we first analyzed upstream passage efficiency for all non-salmonid orders, including estimates for complete fish communities (Fig. 1). Because the mean upstream passage efficiency for non- 9 salmonid orders did not differ significantly (F[4,35]=0.554, P=0.697), we combined the data for all non-salmonids in subsequent analyses. Mean passage efficiency did not differ significantly between upstream (x̄ =41.7%, SE=4.4, n=61) and downstream (x̄ =68.5%, SE=6.4, n=17) directions (two-way ANOVA: F[1,74]=3.07, P=0.084), but was higher for salmonids (downstream: x̄ =74.6%, SE=6.4, n=14; upstream: x̄ =61.7%, SE=5.9, n=31) than non-salmonids (downstream: x̄ =39.6%, SE=10.7, n=3; upstream: x̄ =21.1%, SE=3.7, n=30) (two-way ANOVA: F[1,74]=15.4, P<0.0005) (Fig. 2). Upstream migrating salmonids used the fishways primarily during the day in 16 of 17 studies (Sign test: P<0.0005), whereas non-salmonids showed no preference (5 during the day vs. 5 at night; Sign test: P=1.00). Furthermore, upstream passage efficiency did not differ significantly between continents (data not shown; twoway ANOVA: F[2,50]=0.50, P=0.608) but did differ significantly between salmonids and non-salmonids (see below; two-way ANOVA: F[1,50]=11.31, P=0.002). The type of fishway had a significant effect on passage efficiency (two-way ANOVA: F[4,63]=4.781, P=0.002) (Fig. 3), as did order of fish (two-way ANOVA: F[1,63]=13.496, P<0.0005), with salmonids having a higher efficiency than non-salmonids; there was no significant interaction between species of fish and type of fishway (two-way ANOVA: F[4,63]=0.445, P=0.776). Pool & weir fishways did not differ significantly from pool & slot, or natural fishways (Tukey post hoc test, all P-values > 0.14), but had higher passage efficiency than Denil fishways and fish locks/elevators (Tukey post hoc test, all P-values <0.0005 respectively); no other comparisons differed significantly from one another. 10 Because fish locks/elevators differ fundamentally from the other types, in that they do not require fish to swim upstream under their own effort (Clay 1995), they were excluded from further analysis of the effects of technical characteristics. To determine how pool & weir, pool & slot, natural, and Denil fishways differed, one-way ANOVAs were used to compare three basic technical characteristics: length, slope, and velocity (Table 2). Total fishway length differed significantly between types (F[3,25]=6.347, P<0.0005), as did the slope (F[3,26]=12.279, P<0.0005) and water velocity (F[3,16]=4.091, P=0.025). For all three characteristics, pool & weir, pool & slot, and natural fishways did not differ significantly (Tukey post hoc test: all P-values > 0.086), but all three differed significantly from Denil fishways (Tukey post hoc test: all P-values < 0.046), except for water velocity between natural and Denil fishways (P=0.250) and length between pool & slot and Denil fishways (P=0.234). Fishway slope was negatively correlated with fishway length and velocity, whereas fishway length was positively correlated with velocity (Table 2b). For all fishways that required fish to swim upstream under their own effort, upstream passage efficiency decreased as the slope increased (ANCOVA: F[1,34]=6.45, P=0.016; Fig. 4a), increased with the length of the fishway (ANCOVA: F[1,38]=4.79, P=0.035; Fig. 4b), and increased with the water velocity through the fishway (ANCOVA: F[1,24]=6.47, P=0.018; Fig. 4c). In all cases, efficiency was higher for salmonids than nonsalmonids (fishway length: ANCOVA, F[1,34]=12.34, P=0.001; slope: ANCOVA, F[1,38]=6.01, P=0.019; water velocity: ANCOVA, F[1,24]=4.17, P=0.052). Upstream passage efficiency also increased with total fish length for salmonids (Pearson’s correlation: r=0.737, n=19, P<0.0005), but not for non-salmonids (Pearson’s correlation: 11 r=0.092, n=17, P=0.724, Fig. 4d). Species of salmonid was not related to passage efficiency once fish length was included in the model (ANCOVA: F[7,10]=0.87, P=0.56). Total fish length was not significantly related to downstream passage efficiency for salmonids (Pearson’s correlation: r=-0.321, n=9, P=0.400) and there was insufficient data (n=1) to analyze the non-salmonids. Passage time differed significantly between orders of fish (one-way ANOVA: F[1,15]=46.353, P<0.0005), and was longer for non-salmonids (x̄ =5.52 days, SE=1.61, n=3) than for salmonids (x̄ =0.87 days, SE=0.10, n=14). However, fallback after successful upstream passage did not differ significantly between salmonid species(oneway ANOVA: F[3,26]=0.80, P=0.505) (Fig. 5). Mean attraction efficiency (x̄ =65.1%, SE=7.6, n=12) was significantly higher than entrance efficiency (x̄ =39.6%, SE=8.1, n=11) (one-way ANOVA: F[1,21]=5.60, P=0.028), but there was insufficient data to perform any further statistical analysis on species-specific trends. Attraction and entrance efficiency were negatively related to the slope of the fishway, (ANCOVA: F[1,13]=5.48, P=0.036, Fig. 6a), and positively, but not significantly, related to the length of the fishway (ANCOVA: F[1,16]=2.345, P=0.145, Fig. 6b). In both cases, attraction efficiency was higher than entrance efficiency (ANCOVA: F[1,13]=9.99, p=0.008; F[1,16]=8.13, P=0.012, respectively). There was insufficient data to study the effects of water velocity on attraction and/or entrance efficiency (n=4, and 3, respectively). To determine the best predictors of fish passage efficiency, we used an information-theoretic approach (Burnham et al. 2010) to select the best model. Of the models analysed using the complete data set, three had AICc values within 2 of the best 12 model (Table 3a). However, the only single-factor model in this group included order of fish (i.e. salmonids versus non-salmonids) as the best predictor of upstream passage efficiency (Table 3a). Type of fishway alone was not supported, however models that included species and type were also well supported. In the reduced data set that included technical characteristics of the fishway, three models emerged with AICc values within 2 of the best model. The only single factor model in this group included length of the fishway as the best predictor of passage efficiency. However, models that also included order of fish and type of fishway could not be ignored (Table 3b). Discussion To mitigate habitat fragmentation caused by anthropogenic barriers, upstream passage facilities should allow 90-100% of migrating adult fish to pass in a safe and rapid manner (Ferguson et al. 2002; Lucas and Baras 2001) . Our analysis indicated that the mean upstream passage efficiency of only 41.7% was well below this desired goal. While many studies reported passage efficiencies at facilities within the desired ranges, many more reported much lower efficiencies, including several facilities with 0% passage efficiency (Laine et al. 1998; Bunt et al. 2000; Knaepkens et al. 2006; Mallen-Cooper & Stuart 2007). Even though the average downstream passage efficiency of 68.5% was slightly higher than upstream, it was clear that current fishways are not achieving their primary conservation goal of restoring the connectivity of freshwater ecosystems. Regardless of fishway type, salmonids were more successful than non-salmonids at bypassing barriers. Indeed, order of fish was the best overall predictor of upstream 13 passage efficiency in the complete data set, and was included in the best supported models in the reduced data set. The relative success of salmonids is likely related to their strong swimming ability (Webb 1975) and to the design of fishways, which often target adults of commercially important species, such as anadromous salmonids (Larinier 2001; Calles and Greenberg 2005; Parsley et al. 2007; Schilt 2007). For example, in the Columbia and Snake Rivers, fishways are well designed for passing anadromous salmonids, whereas non-salmonids are unable to use the fishways effectively (Moser et al. 2002a,b). As the goal of conservation activities shifts from a maximum-sustainableyield to a biodiversity-protection approach, it will be increasingly important to consider the swimming abilities and behaviour of the complete fish community (Oldani et al. 2007). Given this new conservation perspective, our analysis highlights the need for more research on non-salmonid species. Our results indicate that the type of fishway was an important parameter in most well supported models predicting passage efficiency. Pool-type fishways had the highest efficiency, followed closely by natural fishways, whereas fish locks/elevators and Denil fishways were less efficient. When a reduced data set was analyzed, including the characteristics of the three main types of fishways, fishway length was the best predictor of upstream passage efficiency. Curiously, longer fishways had higher passage efficiency. All else being equal, a longer fishway would increase the energy expenditure of the migrating fish, and thus decrease passage efficiency. However, energy expenditure may be more related to fishway steepness than length (Mallen-Cooper & Stuart 2007), and fishway length and slope were negatively correlated. Hence, our findings were in agreement with those showing that fish passage decreases with the slope of the fishway 14 (Mallen-Cooper & Stuart 2007). The poor success of Denil fishways may be related to the shortness (x̄ =14.2 m) and steepness (x̄ =14.5%) of these structures. Water velocity through the fishway was positively correlated with upstream passage efficiency, but too few data were available for further analyses. Although the energy expenditure of migrating fish increases with swimming speed and water velocity (Webb 1975), higher water velocities attract more fish to the fishway (Weaver 1963). The inability of fish to locate fishway entrances results from the numerous sources of water discharge in the dam tailrace, such as undesirable eddies, boils, and upwellings that act as directional stimuli and confuse salmon (Clay 1995; Brown et al. 2006). While fishways require a constant flow of water through their structure, resulting in lost production of hydroelectric power, the loss is typically a fraction of the annual capital cost of the fishway (see below; Clay 1995). Denil fishways also had the lowest mean water velocities, likely resulting in poorer attraction of potential migrants. Our findings may have implications for the assessment of infrastructure development in countries with strict environmental policies. For example, in Canada the Fisheries Act requires proponents of new projects to achieve ‘No Net Loss’ of the productive capacity of habitats for fisheries (Quigley and Harper 2006). As such, the construction of an effective passage facility may be required whenever a dam or barrier is constructed. A free standing, concrete reinforced, pool-type fishway that takes no advantage of natural contours costs about $2,600/m3 (2011 U.S. dollars), with annual expenses of about 1-2% of the capital cost (Clay 1995). A fishway that can take advantage of any natural contours will reduce these costs accordingly. Denil fishways, often the cheapest option (Clay 1995), cost about $124,000 (2011 U.S. dollars) per 15 vertical meter (Erkan 2002) with minimal maintenance and operation costs (Clay 1995). Fish locks and elevators cost roughly $2.4 million (2011 U.S. dollars) to install, with annual maintenance charges of 5% of the capital cost (Clay 1995). While Denil fishways are generally the most economical option, they also had the lowest mean passage efficiency, approximately 16%. Our analysis suggests that the more expensive pool and natural fishways were also the most effective. However, only the very best designed fishways are approaching 100% success, which would satisfy the ‘No Net Loss’ policy of Canada. Indeed, the average fishway in our data set allowed only 62% of salmonids and 21% of non-salmonids to pass upstream. Application of the precautionary principle would imply that the average barrier equipped with a fishway reduced the productive capacity of the ecosystem by about 50%. The design of a fishway is highly relevant to the efficiency of its performance, affecting its use by fish, and the species that it may pass (Agostinho et al. 2002). Many currently installed fishways have technical characteristics that are poorly matched to the ichthyofauna present, exemplified by undesirably low mean passage efficiencies. These characteristics need to be measured and reported more frequently, particularly in Canada (see Hatry et al. in press), if we are to develop more effective fish passage facilities. Acknowledgements We thank the Natural Sciences and Engineering Council of Canada (NSERC) and Concordia University for their support in the form of an NSERC Discovery grant to J.W.A.G. and an NSERC Undergraduate Student Research Award to M.J.N. 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Family Salmonidae Entire Community Order Salmoniformes - N Upstream N Downstream 31 14 9 - Clupeidae Clupeiformes 8 2 Percidae Perciformes 6 - Cyprinidae Cypriniformes 6 - Petromyzontidae Petromyzontiformes 5 - Catostomidae Cypriniformes 3 - Cottidae Scorpaeniformes 3 - Percichthyidae Perciformes 3 - Centrarchidae Perciformes 2 - Acipenseridae Acipenseriformes 1 - Esocidae Esociformes 1 - Lotidae Gadiformes 1 - Balitoridae Cypriniformes 1 - Cobitidae Cypriniformes 1 - Retropinnidae Osmeriformes 1 - Galaxiidae Osmeriformes 1 - Characidae Characiformes 1 - Anostomidae Characiformes 1 - Prochilodontidae Characiformes 1 - Loricariidae Siluriformes 1 - Terapontidae Perciformes 1 - 34 Anguillidae Anguilliformes - 35 1 Table 2 (a) Mean values of the primary technical characteristics for four types of fish passage facility, and (b) Pearson’s correlation coefficients (N) between the three characteristics. (a) Type of fishway Length (m) SE n Slope (%) SE n Velocity (m/s) SE n Pool & weir 190.3 ± 71.4 7 8.1 ± 0.75 11 1.78 ± 0.18 9 Pool & slot 175.6 ± 101.8 5 6.3 ± 2.42 3 2.07 ± 0.33 3 Natural 202.9 ± 41.4 10 4.2 ± 1.11 9 1.80 ± 0.50 2 14.2 ± 5.3 8 14.5 ± 1.47 10 0.89 ± 0.21 7 Denil (b) Length (m) Slope (%) -0.703** (23) Velocity (m/s) -0.474 (13) Velocity (m/s) 0.594* (13) 36 (a) Table 3 Model selection using Akaike’s information criterion adjusted for small sample sizes (AICc) to assess variation in upstream passage efficiency using a) the complete data set, and b) a reduced data set incorporating technical characteristics of the fishway (length and slope). Order denotes salmoniformes vs. all other orders, whereas type refers to pool & weir, pool & slot, natural, and Denilfishways. a) Complete Data Set n=47 AICc ∆i Order a 53.39 0.00 0.52632 Order + Type 55.04 1.65 0.23077 Order*Type 55.27 1.88 0.20580 Intercept 58.64 5.25 0.03816 Type 58.83 5.44 0.03474 b) Reduced Data Set n=26 AICc ∆i Length + Order*Type 25.45 0.00 0.29175 Order*Type 26.26 0.81 0.19436 Order + Length 27.01 1.55 0.13405 Length 27.53 2.08 0.10300 Order + Type + Length 28.69 3.23 0.05787 Slope + Order*Type 28.84 3.39 0.05363 Length + Slope + Order*Type 29.12 3.67 0.04656 Type + Length 29.32 3.87 0.04211 Order + Type 30.87 5.42 0.01944 a 37 wi wi a Order 31.89 6.44 0.01166 Type 32.12 6.67 0.01039 Order + Slope 32.32 6.86 0.00943 Slope 32.75 7.30 0.00757 Order + Type + Length + Slope 33.09 7.64 0.00641 Intercept 34.00 8.55 0.00406 Order + Type + Slope 34.11 8.66 0.00385 Type + Slope 34.36 8.91 0.00339 The selected model. 38 Figure Legends Figure 1 Mean (±SE) upstream passage efficiency for all orders of fishes with N≥5. Entire community refers to studies that measured the entire non-salmonid community with no distinction between orders. In all figures, numerals above the bars represent sample sizes. Figure 2 Mean (±SE) passage efficiencies for up- and downstream migration at fish passage facilities for salmonid and non-salmonid fishes in North America, Europe, and South America/Australia. Figure 3 Mean (±SE) upstream passage efficiency for migration at five types of fish passage facility, for salmonid and non-salmonid fishes. Figure 4 Upstream passage efficiency, for salmonid and non-salmonid fishes in relation to a) fishway slope, b) fishway length, c) water velocity through the fishway, and d) total fish length. Lines represent least-squares regressions. Figure 5 Mean (±SE) percentage of fish that fell back at fishways, defined as the percentage of fish that passed back downstream via spillways or turbine intakes, after the successful ascension of a fishway, for four different species of salmonids. SP-SU chinook are spring-summer running chinook, fall chinook are fall running chinook. Figure 6 Upstream attraction and entrance efficiencies in relation to a) fishway slope and b) fishway length for all fish species. Lines represent least-squares regressions. 39 Figure 1: 40 Figure 2: 41 Figure 3: 42 Figure 4: 43 Figure 5: 44 Figure 6: 45